In a laser-based additive manufacturing (“LBAM”) method, a laser beam forms a functional component through a process of material addition. More specifically, a laser beam melts a relatively small, localized portion of a surface of a sacrificial substrate component and/or a portion of the functional component itself. Depending on the material, a relatively small, localized molten pool of metal, ceramic, and/or carbide is formed. A solid powder including metal, ceramic, and/or carbide is delivered by a powder delivery system and deposited over a portion of the surface of the component, including the molten pool. When the powder contacts the molten pool of material, the powder is also melted. Removal of the laser beam from the component allows both the molten pool and the melted powder to cool, thereby adhering or fusing the powder to the component. By this method, a layer of material is effectively added to the component. Thus, a complete functional component may be obtained through the application of multiple layers of material.
Precise control of a feeding rate of the powder delivered to the molten pool in the LBAM method often results in a component part having chemical and/or mechanical properties closer to the desired properties than does imprecise control. Precise control includes the ability to deliver the powder at a relatively small feeding rate and/or at a relatively continuous feeding rate, and/or to change a desired feeding rate over a relatively short time interval.
It is known to use a commercially available powder delivery system that is optimized for another manufacturing process; such as a thermal spraying process, in the LBAM method. However, the thermal spraying process powder delivery system is optimized for the delivery of powder at a relatively higher feeding rate (e.g., 100 to 1000 times) than that used in the LBAM method. As a consequence, the feeding rate from such a known powder delivery system generally varies by an amount that is greater than a maximum required feeding rate in the LBAM method. Thus, such a known powder delivery system suffers from the disadvantage that the powder cannot be precisely delivered in the LBAM method.
It is also known to use a powder delivery system including a metering device to which powder is discretely (i.e., non-continuously) fed or dosed from a hopper. In such a system, the powder is delivered from an output of a hopper into one or more discrete pockets formed in a top surface of the metering device, the portion of the top surface that does not include the discrete pockets being in contact with the hopper output. However, such a known powder delivery system also suffers from the disadvantage that the powder cannot be precisely delivered because the powder is discretely fed or dosed to the metering device.